1. Field of the Invention
This invention relates to a shoe sole for a leg apparatus that serves as an ambulatory apparatus for persons paralyzed in both legs.
2. Description of the Prior Art
Injuries to the cervical or spinal vertebrae caused by automobile accidents, falls and the like can paralyze the upper and lower limbs. Many persons handicapped by such injuries are instantaneously committed to life in a wheel chair. Although wheelchairs provide the handicapped with good mobility, they have numerous drawbacks from medical and psychological viewpoints. Among the ambulatory apparatuses devised for overcoming these disadvantages of the wheelchair is the parawalker developed in the U.K. The user of,this apparatus has all of his or her lower body aside from the hip joints immobilized and moves forward by twisting the upper body. Since ambulation by twisting requires clearance between the free leg and the floor, the user has to tilt his or her body by a large angle. Walking therefore becomes a very strenuous activity. It is possible to eliminate the need for large body tilting and reduce the burden on the user by shortening the length of the free leg from the time it leaves the floor and lengthening it again when it comes in contact with the floor to once more serve as the supporting leg. As a mechanism for achieving alternate lengthening and shortening of the legs there has been developed a leg apparatus able to vary the thickness of a shoe sole. (See Japanese Patent Public Disclosure Hei 4(1992)-352961, for example.)
FIG. 7 shows such a sole developed earlier for enabling thickness adjustment. As illustrated, the sole 100 has a two-tier sole structure consisting of an upper sole member 101 and a lower sole member 102 connected by a pair of linkages 106 each constituted of a pair of links 103 and 104 and a pivot 105. The thickness of the sole 100 can be changed by bending land straightening the linkages 106 to move the upper sole member 101 and the lower sole member 102 toward and away from each other. As indicated by reference numerals 107 in FIG. 7, pneumatic cylinders or the like can be used as the actuators for bending and straightening the linkages 106. Since the actuators 107 are mounted between the upper and lower sole members 101, 102 of the sole 100, however, they increase the weight of the sole 100 and place a greater burden on the user. In addition, the presence of the actuators 107 between the upper and lower sole members 101, 102 limits the degree to which the thickness of the sole 100 can be reduced.
The present invention was accomplished in view of the foregoing circumstances and has as its object to provide a leg apparatus shoe sole which enables the thickness of the sole to be changed with ease, does not place a heavy load on the feet of the user, is simple in structure and allows great reduction of the thickness of the shoe sole on the free foot.